1. Field of the Invention
The present invention relates to a method for forming a borosilicate glass film (hereinafter referred to as a BSG film) by means of a CVD method.
2. Description of the Prior Art
Up to now, a borosilicate glass film (BSG film) has been formed by means of a CVD method under the following conditions of gas and depositing temperature:
(1) SiH.sub.4 +B.sub.2 H.sub.6 +O.sub.2 (400.degree. C.) PA1 (2) TEOS+TMB or TEB+O.sub.2 (750.degree. C.) PA1 (3) TEOS+TMB or TEB+O.sub.2 (400.degree. C.), and the like.
However, the as-depo film according to the above CVD method is mixed with B.sub.2 O.sub.3 +SiO.sub.2, and is not of glass structure. The as-depo means a state which is immediately after the deposition. This film is poor in denseness and high in hygroscopicity. Particularly, when the concentration of boron in the film exceeds 5 to 6 wt %, it abruptly becomes high in hygroscopicity. Therefore, it is not suitable for application to manufacturing process of a semiconductor device and the like.
To improve this problem, the film can be changed to glass structure by heating the as-depo film at a high temperature of 800.degree. C. or higher.
However, a high-temperature heat treatment needs some extra equipment and requires much time and labor, and some processes and interconnection materials used for manufacturing a semiconductor are subject to restrictions due to its treatment. Thereby, this method for forming a film has been kept from being applied to a process for manufacturing a semiconductor device.